Various batteries, including lithium-ion, lead acid and nickel-metal hydride variants, may be configured to have rechargeable attributes. Such batteries may be used as a rechargeable energy storage system (RESS) as a way to supplement or supplant conventional internal combustion engines (ICEs) for automotive applications. The ability to passively store energy from stationary and portable sources, as well as from recaptured kinetic energy provided by the vehicle and its components, makes batteries (in general) and rechargeable batteries (in particular) ideal to serve as part of a propulsion system for cars, trucks, buses, motorcycles and related vehicular platforms. Several such batteries may typically be combined in a module, section, or pack to generate the desired power and energy output.
Because an energized battery cell, module, section or pack is capable of producing large amounts of energy, there may be circumstances where depowering is desired. For example, where an energized battery is to be stored, transported, or handled, it may be desirable to depower the battery. Conventional methods of depowering an intact rechargeable battery involve using an electrical circuit or a load bank. Under circumstances where such conventional methods are not applicable, feasible or limited, an ionically-conductive aqueous solution, dispersion or suspension can be used to depower the battery. In one form, such solution may include sodium chloride, sodium sulfate, or other salts. While useful for providing an electrolytic medium and the related depowering of electric batteries, such solutions can lead to corrosion of sensitive battery components (such as tabs, leads or the like) and the evolution of gaseous byproducts (specifically, hydrogen, oxygen and chlorine) during battery depower. Corrosion of the positive end of a battery complicates the depowering process and can allow for the aqueous solution to enter the battery and cause severe damage to the battery electrodes. Moreover, such solutions can lead to temperature spikes during the depowering process, thereby subjecting battery separators, electrodes, electrolytes and other components to damaging temperatures.
The present inventors have discovered new ways to depower automotive batteries. One way that a battery can be sufficiently depowered is by applying to the battery carbon black or carbon fiber suspended in a substantially non-ionic aqueous medium. Such methods are dependent upon the conductivity, viscosity, component solubilities, and component concentrations of the depowering medium used therein. Given such factors, there is a possibility that an undesirable rate or duration of depowering may occur when such methods are employed. Also, such methods may not be suitable for rapid depowering due to the upper conductivity limits of the carbon medium used. Additionally, because such methods tend to require a high level of carbon loading in order to achieve the desired level of conductivity, the viscosity of the depowering medium may rise to a level that makes its use impractical. Moreover, the use of dispersing agents (for example, sodium carboxymethyl cellulose) to keep the carbon black or carbon fiber suspended in the aqueous medium may exacerbate the viscosity problem, as well as increase manufacturing costs.